Variable-speed alternating-current motor.



QXR-tneweo R. D. MERSHON. VARIABLE SPEED ALTERNATING CURRENT MOTOR.

APPLICATION FILED MAY 28,1906.

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: 5 hi 6 Ho; 1 1MP R. D. MERSHON. VARIABLE SPEED ALTERNATING CURRENTMOTOR.

APPLICATION FILED MAY 28,1906.

Patented Aug. 17, 1909.

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Qvi [Me 5 ac o R. D. MERSHON. VARIABLE SPEED ALTERNATING CURRENT MOTOR.APPLICATION FILED MAY 28,1906.

- 93 l, 1 36. Patented Aug. 17, 1909.

i 3SHEETS-SHBET 3.

QM [Me a a e A RALPH Di MERSHIDN, OE'NEW YORK, N. Y.

VARIABLE-SPEED- ALTERNRTINWCURRENT MOTOR.

Specification of Letters Patent.

PatentedAug. 17, 1909.

Application filed. Kay 28. 1906. Serial No. 319,034.

To all whom it ma concern:

Be it. known that I, RALPH DL hlEnsHoma citizen of the UnitedStates,residing at New York, in the county and State ofiNcw York, have inventedcertain new and useful improvements in Variable-SpeedAlternatingtlurrent Motors. of which the following is a specification.reference being had to the drawing accompanying and forming part of thesame.

My invention relates to alternating current motors in which the speedisvarled by so-called rheostat control of the secondary, and hasvfol-its chief object to provide a motor capable of such speed regulationbut without electrically connecting the rlieostats, condensers,reac'tances, or other controlling devices with the secondary.

The present invention, which is a speciesof the generic inventiondescribed in my c0- pending application, Ser. No. 319,033, will be morereadily understood if an explanation be first given of a certainprinciple of operation made use of therein. This principle willitself bemorereadily comprehendedwhen explained with the help of diagrams,

and for that purpose reference isnow made to the annexed drawings,wherein,

Figure 1 shows a machine having a 2-pole primary element and a l-polesecondary element. Fig. 2 shows a similar machine, but having chokecoils or auto-transformers in the connections of the secondary. Fig. 3-

shows a l-pole primary and a 4-pole secondary, withlchoke'coils orauto-transformers in the connections of each. Fig. 4 shows a--poleprimary, the four poles being produced in a different manner from themethod shown in Fig. 3, but with equivalent results for the purposes ofthis invention. Fig. 5 shows a motor with 2 (i-pole primary and a.2-pole secondary. Fig. 6 shows a simple andconvenient embodiment of thepresent invention.

Let us suppose that with a primary m which a given number of poles isproduced, for example two, we employ a t-pole secondary whose polewindings are in series or the equivalent. The primary will then have noreal efiecton the secondary, since adjacent mils being wound in oppositedirections, the

resultant of; the E. M. Fs. produced thereinwill be zero. Conversely, a4- 'ole primary Will have no efieet on a 2-po e secondary whose polewindings are in series on theequivalent thereof, for, while each oftheioun poles in the primary. wallsend influx.

= scribed.

' dependent,

and may.

through. the secondary structure there will be at all times oppositefluxes through.- each pole' of the- Z-pole secondary. winding, and no.E. M; F. wili nesult.

Referring now to Fig: l, P indicates a primary in which two poles areproduced, and S isa lt-pole secondary, the direction of the currentinthe former at! a given instant being indicated by the arrows on theleads, and the corresponding flux by dottedlines. In this secondary,however, current can be produced, for the reason that it is not woundwith its poles in series or the equivalent. Suppose now-that; we insert:in each secondary connection a choke-coil or auto-transformer, tapped atits center, as in Fig. 2. Such a choke coil will: not allow-cum'ent;,-(.except that for magnetizing it), to

flow through.its-two-halves in 58111655,.bllt will allow equalcurrentsto flow from. the ends of the coilzto the middle and-out throughthe tap thereat', and will alsoallow current flowing. in throughtlie'tap to divide at the and flow through the two= halves thereof.Hence,. in Fig. 2 the Z-pole primary can cause no current flow exceptthat for-magnetizing the choke coils or auto-transformers.

If new we employ with such a secondary awlrpole primary (for exainpleasin. Fig. 3), current will flow in each half of: each autotransformer andthrough the taps. quentiyi, although the polewindings of the secondaryin Fig. are not in series, never- (louse thelessit is by reason of itspeculiar con.- nections equivalent (except for the magnet iylingzcum'entin the auto transformers) to a ls-pole secondary whose pole windings arein: series.

their middle points is made to obtain a i-pole'w inding fronnthe closedcoil winding of? the primany. If the anto-t ransfomiers be omitted and:opposite points of the winding. might be connected by a simple conduo-tor the arrangement; would be equivalent t'oa i-pole multiplewinding;.but would not accomplish certain results hereafter de- It'. isevident from the foregoing that; at 4 pole primary and a 2polesecondary, or vice versa, may be inductively 1nor,v stated moregenerally,. a primary winding for one number of poles may be inductivelyindependent of a secondarywinding for another number of poles. Thisprinciple is availedof in my invention, be aptly termed the principle ofcoil It will be observed that in. Fig. 3 asimilar use ofauto-transformers tapped at non-mutual poles or non-mutual .windings. Itmay also be stated generally that any windings, whose pole windings arein series or the equivalent thereof as described above, are non-mutualif the larger number of poles divided by the smaller gives 2 or a powerthereof as the quotient. Thus 2-pole and t-pole windings of the kinddescribed are non mutual, also 2 pole and 8 pole, (3-pole and l2-pole,12-pole and 24-pole, etc, Other pole numbers, having a different ratioto each other, as l and 6, may be non-mutual, as can easily bedetermined, but generally speaking the combinations most convenient forthe purpose hereinafter described will be found to be those in which theratio is 2 or a power thereof, as stated above. With still other ratios,as for example, in the case of (i-pole and 2-pole windings, the two maybe partly non-mutual. mentioned is illustrated in Fig. 5, in which theprimary P of the motor has six poles while the secondary S is connectedfor two poles by the conductore. It will be seen that only a part of themagnetization of the (i-pole primary can be effective on the 2-polesecondary. However, to the extent that the former is not effective onthe latter they are non-mutual. A combination of this kind, that is, onein which the non-mutuality is only partial, can be used for the purposesof my invention, but with results less satisfactory than withcombinations in which the windings are wholly non-mutual. By analogywith the foregoing, windings which are not electro magneticallyindependent may be said to be mutual to each other.

It is not necessary thatauto-transformers, connected as described above,be. used to make windings of the closed coil type illustrated,non-mutual. The same results can be obtained by using separatesecondaries on the supply transformers, in the case of the primaryelement of the motor; and, in the case of the motor secondary, by usingseparate secondaries on a transformer connected thereto. This method isillustrated in F 41, in which 8, s are the separate secondaries on thesupply transformer T. With open coil windings with their pole windingsin series no auto-transformers are required to obtain the condition ofnon-mutuality, but this method requires the use of a plurality ofwindings and is in eneral not so desirable as the methods wlnch may beemployed with a single winding.

Keeping the above explanation in mind the invention will be readilyunderstood from a description of a simple embodiment thereof, shown inFig. 6. In this re, P desi nates the primary winding, an S and Sesignate two secondary windings, both secondaries being preferably onthe samerotating part. The windings of the motor mayv be of the drum,polar, or any other clear.

means of conductors d, d and v result is, according to the principle ofthe well known method of concatenated con- .type, as for example thesingle ring windmgs shown. G indicates the source of current, which maybe single or polyphase, for example two-phase as shown, the two phasesbeing for convenience designated A and B. The leads from the source areindicated by Z, Z and Z Z for the two phases A'and B respectively. Fromthese leads the currents divide through choke coils or auto-transformers0 to the motor leads Z*, Z, Z, Z", Z, Z, Z, Z, which are connected tothe primary at the proper points to produce four poles therein. One ofthe secondaries, as S, is also connected for four poles, as shown,through choke coils a. The other secondary, S, is provided at fourpoints with connections for two poles, but the connections lead .to themiddle points of the choke coils a, as shown. The instance just Theoperation of the motor will now be The currents in the primary P, inwhich there are four poles, have no-etfect 011 the secondary winding S,(since the "latter is connected for only two poles), but do xaffect thesecondary winding S, which is connected for four poles. The currents inthe latter secondary winding, however, flow into the other secondary, S,through its two-pole connections from the auto-transformers. The lattersecondary winding thus becomes a primary with two poles, and hence tendsto induce current 1n the primary 1 which would flow out from the samethrough motor leads Z Z, Z, Z, which constitute a two-pole connection.The circuits of these currents from the windings P are, however,practically open, since the choke coils 0 prevent the currents fromflowing from one lead to the other, and consequently no work current canflow in the secondaries. It is therefore necessary to close' one ormore'of these circuits, from the windin P, as by (i The trol, that therotating element rotates at six-pole synchronous speed although thereare only four poles in the motor primary P, produced directly from thesame source C.

Inserted in the conductors d, and d, (Z and d are rheostats R, R, orcondensers, reactances or other controlling devices or combinations oftwo or more of these, according to the results desired, by which thecurrents in the conductors mentioned, from the motor primary P, may becontrolled or modified as desired. The modification of these currentscorrespondingl modifies the currents in the secondary, e ecting acorrespondin change of speed of the rotating element. Ty providing threewindings or secondaries on the inner element, one conneeted for twopoles, one for four, and one for eight, a synchronous speedcorresponding to twelve polesand another corresponding to ten poles canbe obtained, when eight poles are produced in the primary or outsideelement, while by changing the number of poles in the latter to four asynchronous speed corresponding to six poles can be ob tained. withrheostatic control of each through the outside element, entirely withoutthe use ofcollector rings. ()ther arrangements might benicnt-ioned, withfewer or more windings. or other numbers of poles, or both, giving otherspeeds, with rheostatic control through the outer element, it beingclear that the invention is in no way limited to the specific formsherein referred to.

It is immaterial; which pole connections to the outside elements areused for the rheostat and which for the supply of current from thesource in producing it given sym-hronous speed, that is, for example,the outside. element may have eight poles,vwith the rheostat connectedthrough el-pole connections, or vice versa, and the same speed will beproduced, corresponding to twelve poles. ()ther speeds can of course beobtained by employingmore windings, either primary or secondary, orboth, or other pole numbers, or suitable combinations of these, asdesired.

The motor showirin the drawing is supplied with polyphase current fromthe source of power, but it is clear that the invention is applicable tosingle phase apparatus as well. in either case, however, the connectionsfrom secondary to secondary would preferably be polyphase. Nor isitnecessary to connect the leads from the source to single points in theprimary; instead, they may be connected-at a plurality of points foreach, as for the purpose of'obtaining some particular tlux distributionin accordance with the invention described and claimed broadly in mycopending application, vSer. No. 367,529. The type of winding orwindings employed is also immaterial, whether ring, as shown, drum, orpolar, open or closed coil, it being observed that with closed coilwindings the pole windings thereof must be in series or the equivalent,as explained hereinbefore, to produce the condition of nonmutualitywhere desired.

'hat I claim is:

1. In an alternating current machine, the combination of a. primarywinding haying poles produced therein; a secondary element adapted ,tohave current induced therein corresponding to poles in the said primarywinding, and capable of inducing other poles in the said primarywinding; and means for closing the circuit or circuits of currentinduced in the said primary winding; as set forth.

2. In an alternating current machine, the combination of a primarywinding having poles produced therein; a secondary element adapted tohave current induced therein corresponding to poles in. the said primarywinding; and capable 0t inducing other poles in the said primarywinding; means for closing the circuit or circuits of current induced inthe said prin'iary winding; and means for regulating such inducedcurrentor currents; as set forth.

3. In an alternating current machine, the combination of a primarywinding having poles produced therein; a. secondary element having aplurality of windings, a portion of said plurality of windings beingadapted to have current induced therein corresponding to poles in thesaid; primary winding, and a portion being adapted to induce other polesin the said primary winding; and means for closing the circuit orcircuits ofcurrent inducedv inthe said primary winding; as set. forth.

4. In an alternating current machine, the combination. of a primarywinding having poles produced therein; a secondary element haivingaplurality ofwindings, a portion of said plurality of windings beingadapted to have current induced therein correspondingto poles-in thesaid primary winding, and a portion being adapted to induce other polesin the said primary winding; means for closing the circuit or circuitsof current induced in the said primary winding; and means for regulatingsuch induced current; as set forth.

5. In an alternating current machine, the combination of a primarywinding; :1 plurality of interconnected secondary windings, a portionthereof being adapted to have current induced therein by current fromthe said primary winding, and a'portion adapted to induce current in thesaid primary winding; and means for closing the circuit or circuits ofcurrent induced in the said primary winding; as set forth.

6. In an alternating current machine, the combination of a primarywinding; a plurality of interconnected secondary windings, a portionthereof being adapted to have current induced therein by current fromthe said primary winding, and a portion adapted to induce current in thesaid primary winding; means for closing the circuit or circuits ofcurrent induced in the said primary winding; and means for regulatingcurrent in said circuit or circuits; as set forth.

7. In an alternating current machine, the combination of a primaryelement; a plurality of secondary windings, a portion thereof havingpole connections provided with auto-transformers, and a portion havingpole connections to the auto-transformers; and means for closing thecircuit or circuits of current induced inthe primary element;

. as set forth.

8. In an alternating current machine, the combinatlon of a primaryelement; a plurahty of secondary windings, a portion withauto-transformers, and a portion hav-- ing pole connections to theauto-transformers; means for closing the circuit or circuits of currentinduced in the primary element; and means for regulating current in saidcircuit or circuits; as set forth.

9. In an alternating current machine, the combination of a primaryelement adapted to have poles produced therein; a secondary windinghaving pole connections for a number of poles mutual t0 poles in theprimary element; auto-transformers in the pole connections; a secondarywinding having pole connections from the auto-transformers to produce adifferentnumber of poles; and means for-closing the circuit or circuitsof current induced in the primary element; as set forth.

10. In an alternating current machine, the combination of a primaryelement adapted to have poles produced therein; a secondary windinghaving pole connections for a number of poles mutual to poles in theprimary element; auto-transformers in the pole conesmec nections; asecondary Winding having pole connections from the auto-transformers toproduce adifierent number of poles; means for closing the circuitorcircuits of current induced in the primary element; and means forregulating current in said circuit or cir cuits; as set forth.

11. In an alternating current machine, a secondary element having aplurality of windings, a portion thereof havin pole connections providedwith auto-transtormers and a portion having pole connections to theauto-transformers, as set forth.

12. In an alternating current machine, a

secondary element having a plurality of RALPH D. MERSHON.

Witnesses S'rURGEs S. DUNHAM, RAPHAEL A. WEED.

